Method of producing free cutting steel



Patented June 14, 1938 UNITED STATES PATENT OFFICE METHOD OF PRODUCINGFREE CUTTING STEEL Johannes Haag, Neunkirchen, Germany No Drawing.Applicati No. 86,889. In Germany 8 Claims. 75-58) amorphous sulphur oreven of iron sulphide. This method of adding the sulphur, however, isaccompanied by quite a number-of disadvantages, and in particular thesulphur cannot be mixed sufli- ;ciently intimately with the moltenmetal, this being attributable, among other things, to the dif ferencesin specific gravity.

It is the object of the invention to eliminatethese disadvantages, andfor this purpose the invention is based on the fact that, after tapping,de-oxidizing metal; generally manganese or some other metal which is tobe alloyed with the molten metal is generally added to the molten steel.According to the invention, the said metal, for example manganese, andthe sulphur are not added separately, but together in the form of amixture in the necessary mixing proportion. This mixture is made forexample by stirring manganese metal or ferromanganese in the finelyground state, or even so-called manganese dust, into the molten,thinly-fluid sulphur. Upon cooling, this mixture assumes peculiarly ametallic character, and may be cast conveniently into slabs or pieces ofany desired shape. These pieces are added to the steel bath.

The peculiar metallic character of the solidi fied mixtureis apparentlynot produced by-chemical combination between the sulphur and themanganese, but the manganese in the form of dust is suspended in thesulphur. Since this suspension is also adequate even in the thinly-fluidstate, the mixture may also be added fluid to the steel bath, the sameadvantages being attained. These consist on the one hand in that themixture has a higher specific gravity than has pure sulphur, andtherefore mixes better with the molten steel or penetrates the lattermore rapidly. On the other hand, due to the manganese particles beingsuspended in the sulphur, the ignition temperature of the sulphur isalso raised, or at least its rate of combustion is diminished, wherebythe disadvantages residing in the difficulty of proportioning thenecessary quantities of sulphur due to its rapid combustion, and in theeffect of the burnt sulphur in acting as a carrier of oxygen to the ironand manganese in the bath, are also eliminated.

According to the invention, however, it is preferred to add the mixturein the solidified lump on June 23, 1936, Serial June 24, 1935 form tothe bath, since it is thereby possible to apply a further step forpreventing the combustion of the sulphur by surrounding the lumps orpieces with an envelope protecting them from oxidation. A solution ofwater glass for example, into .which the pieces are dipped, is suitablefor such an envelope. Preferably, however, an

envelope of a reducing substance, such as for:

example paper, will be employed.

The principal advantage of the invention con-' sists inanextraordinarily uniform distribution of the sulphur in the solidifiedsteel ingot. Whereas, in the usual process for the production offree-cutting steel, differences in the sulphur content of the head andbase of the ingot of about 0.10 per cent for a mean content of 0.23 percent are normal, these differences are reduced to half by theapplication of a sulphur-manganese mixture according to the invention,and are practicallyentirely eliminated by the further application of ananti-oxidizing envelope. This advantage is all the more remarkable sincethe differences in the sulphur content in the usual freecutting steelscannot be attributed to segregation" in the usual sense, so thattherefore it has not been possible heretofore to preventthesedifferences by steps capable of producing the socalled re-segregatedsteels.

The invention is described herein with reference to the example of themixture of sulphur and manganese, because this is an excellent form ofapplication. Of course, the idea of the invention may also be utilizedby stirring with the sulphur any other metal to' be alloyed with thesteel bath,

even iron itself, in place of manganese. 7 Example A free-cutting steelof the following contents is to be produced:

C=0.08 per cent.

Mn=0.'70 per cent.

P==0.07 per cent. I v

s=0.200 per cent.

The molten steel which was to be sulphurized has in the finished castsample an analysis with a manganese content of 0.72% and a sulphurcontent of 0.206%. I

180 kilograms of pieces consisting of a mixture of 22% sulphur and 78%manganese and coated with paper, were employed as addition. This mixturewas produced by melting crystalline sul- 1 phur in a pan until it wasthinly fluid; and stirring into the latter finely-ground IS-per centferr 01119118311886.

I claim:

1. Method of producing free cutting steel containing sulphur and alloymetal as ingredients which method comprises mixing molten sulphur and afinely divided alloy metal to form a uniform mixture, shaping the sameinto solid bodies by solidification and introducing the same into themolten steel.

2. A new product for the manufacture of free cutting steels containingsulphur and a deoxidizing alloy metal as ingredients consisting of asolid body produced by solidification of a mixture of molten sulphur anddeoxidizing alloy metal particles.

3. A new product for the manufacture of free cutting steels containingsulphur and deoxidizing alloy metal as ingredients consisting of a solidbody produced by solidification of a mixture of molten sulphur andpulverized manganese.

4. Method of producing free cutting steel containing sulphur and alloymetal as ingredients which method comprises forming a mixture of sulphurand alloy metal by solidifying a melt of sulphur containing substanceswith alloy metal particles distributed therein and adding said mixtureto the molten steel.

5. Method of producing free cutting steel containing sulphur and alloymetal as ingredients which method comprises forming a mixture of sulphurand deoxidizing alloy metal by solidifying a melt of sulphur containingsubstances with alloy metal particles distributed therein and addingsaid mixture to the molten steel.

6. Method of producing free cutting steel con-' taining sulphur andalloy metal as ingredients which method comprises forming a mixture ofsulphur and manganese by solidifying a melt of sulphur containingsubstances with manganese particles distributed therein and adding saidmixture to the molten steel.

7. Method of producing free cutting steel containing sulphur and alloymetal as ingredients which method comprises forming a mixture of sulphurand term-manganese by solidifying a melt of sulphur containingsubstances with ferromanganese particles distributed therein and addingsaid mixture to the molten steel.

8. A new product for the manufacture of free cutting steels containingsulphur and deoxldizing metal as ingredients consisting of a solid bodyproduced by solidification of a mixture of molten sulphur anddeoxidizing alloy metal particles said body being covered by aprotecting envelope.

JOHANNES HAAG.

